November 2022 Volume 4

EQUIPMENT & TECHNOLOGY

Maximizing Energy Efficiency of Induction Systems for Forging

Applications By Joe Stambaugh

Resonance Running inverters off resonance causes derating of inverter devices, resulting in more and/or larger devices to do the same job. When we run inverters close to resonance, they are in their most efficient state, meaning more power output per device. This reduces the number of devices needed to do the same job. Less devices means less inverters, improved efficiency and reduced part costs.

When sourcing induction heating equipment for forging, quoted energy efficiency numbers many times are at best misleading. Generally, the stated efficiency is of the conversion process only and only states the efficiency of the power supply. Power Factor Rarely are the losses due to a poor power factor and the penalties paid to the power company for having a poor power factor considered when purchasing an induction system. When you improve your power factor you save money on your utility bill. A low power factor requires an increase in the electric utility’s generation and transmission capacity to manage the reactive power component caused by inductive loads. Most utility companies charge a penalty to customers with power factors less than 0.95. You can avoid this additional fee by increasing your power factor. By improving your power factor your electrical system’s branch capacity will also increase. Uncorrected power factor will cause power losses in your distribution system. You may experience voltage drops as power losses increase. Excessive voltage drops can cause overheating and premature failure of motors, components, and other inductive equipment. At Ajax TOCCO we have developed technology that improves the power factor on our induction systems to save our customers energy dollars. Harmonics Harmonics are always a problem that goes unrecognized in most large industrial facilities. Harmonics are the result of non-linear loads and can cause other equipment to run incorrectly. Harmonic disturbances caused by some induction power supplies on the same source can cause other equipment to run incorrectly. These disturbances can result in shorter life cycles for motors and other electrical equipment on these lines. When we draw sinusoidal currents, thus reducing harmonics, you save money because of increased up time and reduction in component failure. On larger induction heating systems, the use of a 12-pulse rectifier is a cost effective way of reducing harmonics. A 12-pulse rectifier uses two 6-pulse rectifiers in parallel to feed a common DC bus. A transformer with one primary and two secondary windings creates a 30-degree phase shift between the two current waveforms, which eliminates the 5th and 7th harmonics and reduces THD between 10 and 15 percent.

Electrical Diagram of A 12 Pulse Arrangement

FIA MAGAZINE | NOVEMBER 2022 22